[netbsd-mini2440.git] / crypto / external / bsd / openssl / lib / libcrypto / man / RAND_set_rand_method.3
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136 .IX Title "RAND_set_rand_method 3"
137 .TH RAND_set_rand_method 3 "2007-11-19" "1.1.0-dev" "OpenSSL"
138 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
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140 .if n .ad l
141 .nh
142 .SH "NAME"
143 RAND_set_rand_method, RAND_get_rand_method, RAND_SSLeay \- select RAND method
144 .SH "LIBRARY"
145 libcrypto, -lcrypto
146 .SH "SYNOPSIS"
147 .IX Header "SYNOPSIS"
148 .Vb 1
149 \& #include <openssl/rand.h>
150 \&
151 \& void RAND_set_rand_method(const RAND_METHOD *meth);
152 \&
153 \& const RAND_METHOD *RAND_get_rand_method(void);
154 \&
155 \& RAND_METHOD *RAND_SSLeay(void);
156 .Ve
157 .SH "DESCRIPTION"
158 .IX Header "DESCRIPTION"
159 A \fB\s-1RAND_METHOD\s0\fR specifies the functions that OpenSSL uses for random number
160 generation. By modifying the method, alternative implementations such as
161 hardware RNGs may be used. \s-1IMPORTANT:\s0 See the \s-1NOTES\s0 section for important
162 information about how these \s-1RAND\s0 \s-1API\s0 functions are affected by the use of
163 \&\fB\s-1ENGINE\s0\fR \s-1API\s0 calls.
164 .PP
165 Initially, the default \s-1RAND_METHOD\s0 is the OpenSSL internal implementation, as
166 returned by \fIRAND_SSLeay()\fR.
167 .PP
168 \&\fIRAND_set_default_method()\fR makes \fBmeth\fR the method for \s-1PRNG\s0 use. \fB\s-1NB\s0\fR: This is
169 true only whilst no \s-1ENGINE\s0 has been set as a default for \s-1RAND\s0, so this function
170 is no longer recommended.
171 .PP
172 \&\fIRAND_get_default_method()\fR returns a pointer to the current \s-1RAND_METHOD\s0.
173 However, the meaningfulness of this result is dependent on whether the \s-1ENGINE\s0
174 \&\s-1API\s0 is being used, so this function is no longer recommended.
175 .SH "THE RAND_METHOD STRUCTURE"
176 .IX Header "THE RAND_METHOD STRUCTURE"
177 .Vb 9
178 \& typedef struct rand_meth_st
179 \& {
180 \& void (*seed)(const void *buf, int num);
181 \& int (*bytes)(unsigned char *buf, int num);
182 \& void (*cleanup)(void);
183 \& void (*add)(const void *buf, int num, int entropy);
184 \& int (*pseudorand)(unsigned char *buf, int num);
185 \& int (*status)(void);
186 \& } RAND_METHOD;
187 .Ve
188 .PP
189 The components point to the implementation of \fIRAND_seed()\fR,
190 \&\fIRAND_bytes()\fR, \fIRAND_cleanup()\fR, \fIRAND_add()\fR, \fIRAND_pseudo_rand()\fR
191 and \fIRAND_status()\fR.
192 Each component may be \s-1NULL\s0 if the function is not implemented.
193 .SH "RETURN VALUES"
194 .IX Header "RETURN VALUES"
195 \&\fIRAND_set_rand_method()\fR returns no value. \fIRAND_get_rand_method()\fR and
196 \&\fIRAND_SSLeay()\fR return pointers to the respective methods.
197 .SH "NOTES"
198 .IX Header "NOTES"
199 As of version 0.9.7, \s-1RAND_METHOD\s0 implementations are grouped together with other
200 algorithmic APIs (eg. \s-1RSA_METHOD\s0, \s-1EVP_CIPHER\s0, etc) in \fB\s-1ENGINE\s0\fR modules. If a
201 default \s-1ENGINE\s0 is specified for \s-1RAND\s0 functionality using an \s-1ENGINE\s0 \s-1API\s0 function,
202 that will override any \s-1RAND\s0 defaults set using the \s-1RAND\s0 \s-1API\s0 (ie.
203 \&\fIRAND_set_rand_method()\fR). For this reason, the \s-1ENGINE\s0 \s-1API\s0 is the recommended way
204 to control default implementations for use in \s-1RAND\s0 and other cryptographic
205 algorithms.
206 .SH "SEE ALSO"
207 .IX Header "SEE ALSO"
208 \&\fIopenssl_rand\fR\|(3), \fIengine\fR\|(3)
209 .SH "HISTORY"
210 .IX Header "HISTORY"
211 \&\fIRAND_set_rand_method()\fR, \fIRAND_get_rand_method()\fR and \fIRAND_SSLeay()\fR are
212 available in all versions of OpenSSL.
213 .PP
214 In the engine version of version 0.9.6, \fIRAND_set_rand_method()\fR was altered to
215 take an \s-1ENGINE\s0 pointer as its argument. As of version 0.9.7, that has been
216 reverted as the \s-1ENGINE\s0 \s-1API\s0 transparently overrides \s-1RAND\s0 defaults if used,
217 otherwise \s-1RAND\s0 \s-1API\s0 functions work as before. \fIRAND_set_rand_engine()\fR was also
218 introduced in version 0.9.7.